1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type magnetic transducer for writing and a method of manufacturing the thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought with an increase in surface recording density of a hard disk drive. A composite thin-film magnetic head has been widely used which is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called AMR head or simply MR head. A reproducing head using a GMR element is called GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabit per square inch.
Methods for improving the performance of a reproducing head include replacing an AMR film with a GMR film and the like having an excellent magnetoresistive sensitivity and optimizing the pattern width such as the MR height, in particular. The MR height is the length (height) between the air-bearing-surface-side end of an MR element and the other end. The MR height is controlled by an amount of lapping when the air bearing surface is processed. The air bearing surface is the surface of a thin-film magnetic head that faces a magnetic recording medium and may be called track surface as well.
Performance improvements in a recording head have been expected, too, with performance improvements in a reproducing head. One of the factors determining the recording head performance is the throat height (TH). The throat height is the length (height) of the pole portion between the air bearing surface and the end of the insulating layer electrically isolating the thin-film coil for generating magnetic flux. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
It is required to increase the track density on a magnetic recording medium in order to increase the recording density among the performances of a recording head. In order to achieve this, it is required to implement a recording head of a narrow track structure wherein the width on the air bearing surface of a bottom pole and a top pole sandwiching a write gap is reduced to the order of some microns to submicron. Semiconductor process techniques are employed to achieve the narrow track structure.
Reference is now made to FIG. 31A to FIG. 37A and FIG. 31B to FIG. 37B to describe an example of a method of manufacturing a related-art composite thin-film magnetic head. FIG. 31A to FIG. 37A are cross sections each orthogonal to the air bearing surface. FIG. 31B to FIG. 37B are cross sections each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 31A and FIG. 31B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3-TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material of 2 to 3 xcexcm in thickness is formed for making a reproducing head.
Next, as shown in FIG. 32A and FIG. 32B, on the bottom shield layer 103 alumina or aluminum nitride, for example, of 50 to 150 nm in thickness is deposited through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR film of tens of nanometers in thickness is formed for making an MR element 105 for reproduction. Next, on the MR film a photoresist pattern is selectively formed where the MR element 105 is to be formed. The photoresist pattern takes a shape that facilitates lift-off, such as a shape having a T-shaped cross section. Next, with the photoresist pattern as a mask, the MR film is etched through ion-milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element. Next, on the bottom shield gap film 104 a pair of first electrode layers 106 having a thickness of tens of nanometers are formed, using the photoresist pattern as a mask. The first electrode layers 106 are electrically connected to the MR element 105. The first electrode layers 106 may be formed through stacking TiW, CoPt, TiW, and Ta, for example. Next, the photoresist pattern is lifted off.
Next, as shown in FIG. 33A and 33B, a pair of second electrode layers 107 having a thickness of 150 nm, for example, are formed into a specific pattern. The second electrode layers 107 are electrically connected to the first electrode layers 106. The second electrode layers 107 may be made of copper (Cu), for example. The first electrode layers 106 and the second electrode layers 107 make up leads electrically connected to the MR element 105.
Next, as shown in FIG. 34A and FIG. 34B, a top shield gap film 108 of 50 to 150 nm in thickness is formed as an insulating layer on the bottom shield gap film 104 and the MR film 105. The MR film 105 is embedded in the shield gap films 104 and 108. Next, on the top shield gap film 108 a top shield layer-cum-bottom pole layer (called bottom pole layer in the following description) 109 of about 3 xcexcm in thickness is formed. The bottom pole layer 109 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 35A and FIG. 35B, on the bottom pole layer 109, a recording gap layer 110 made of an insulating film such as an alumina film whose thickness is about 0.2 to 0.3 xcexcm is formed. On the recording gap layer 110 a photoresist layer 111 for determining the throat height is formed into a specific pattern whose thickness is about 1.0 to 2.0 xcexcm. Next, on the photoresist layer 111 a thin-film coil 112 of a first layer is made for the induction-type recording head. The thickness of the thin-film coil 112 is 3 xcexcm. Next, a photoresist layer 113 is formed into a specific pattern on the photoresist layer 111 and the coil 112. Heat treatment is then performed at a temperature of 200 to 250xc2x0 C., for example, to flatten the surface of the photoresist layer 113. On the photoresist layer 113 a thin-film coil 114 of a second layer is then formed into a thickness of 3 xcexcm. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114. Heat treatment is then performed at a temperature of 200 to 250xc2x0 C., for example, to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 36A and FIG. 36B, a portion of the recording gap layer 110 behind the coils 112 and 114 (the right side of FIG. 36A) is etched to form a magnetic path. A top pole layer 116 having a thickness of about 3 xcexcm is then formed for the recording head on the recording gap layer 110 and the photoresist layers 111, 113 and 115. The top pole layer 116 is made of a magnetic material such as Permalloy (NiFe) or FeN as a high saturation flux density material. The top pole layer 116 comes to contact with the bottom pole layer 109 and is magnetically coupled to the bottom pole layer 109 in a portion behind the coils 112 and 114.
Next, as shown in FIG. 37A and FIG. 37B, the recording gap layer 110 and the bottom pole layer 109 are etched through ion-milling, using the top pole layer 116 as a mask. Next, an overcoat layer 117 of alumina, for example, having a thickness of 20 to 30 xcexcm is formed to cover the top pole layer 116. Finally, machine processing of the slider is performed to form the air bearing surface of the recording head and the reproducing head. The thin-film magnetic head is thus completed. As shown in FIG. 37B, the structure is called trim structure wherein the sidewalls of the top pole layer 116, the recording gap layer 110, and part of the bottom pole layer 109 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of the magnetic flux generated during writing in a narrow track.
FIG. 38 is a top view of the thin-film magnetic head manufactured as described above. The overcoat layer 117 is omitted in FIG. 38. FIG. 31A to FIG. 37A are cross sections taken along line 37A-37A of FIG. 38. FIG. 31B to FIG. 37B are cross sections taken along line 37B-37B of FIG. 38.
FIG. 39 is an example of the structure of the top pole layer 116. The top pole layer 116 has a pole portion 116a placed closer to the air bearing surface 120 and a yoke portion 116b placed in a position facing the coils 112 and 114. In the example the width of the pole portion 116a is 1.7 to 2.0 xcexcm. The greatest width of the yoke portion 116b is 40 to 50 xcexcm. Part of the yoke portion 116b closer to the pole portion 116a tapers down to the pole portion 116a. The periphery of the tapered portion forms an angle of 45 degrees, for example, with a surface parallel to the air bearing surface 120.
In the following description the position of the air-bearing-surface-side end of the insulating layer electrically isolating the thin-film coil is called throat height zero position and indicated with TH0. In the example shown in FIG. 39 the distance is 3.0 to 5.0 xcexcm from throat height zero position TH0 to the interface between the pole portion 116a and the yoke portion 116b. 
In order to achieve high surface density recording, it is required that the recording track width, that is, the pole portion width (called pole width in the following description) is reduced. FIG. 40 shows an example of the shape of the top pole layer 116 whose pole width is smaller than that of the top pole layer 116 shown in FIG. 39. In the example the width of the pole portion 116a is 0.8 to 1.2 xcexcm. The pole portion 116a having a width of the submicron order such as 0.4 xcexcm may be implemented in the future.
If the shape of the top pole layer 116 is like the one shown in FIG. 39, the magnetic flux generated from the coils 112 and 114 reaches the tip of the pole portion without saturating before reaching the pole portion.
However, if the pole width is reduced as shown in FIG. 40, for example, the flux is saturated near throat height zero position TH0 and the flux would not fully reach the tip of the pole portion. As a result, the value indicating the overwrite property is reduced to about 10 to 20 dB, for example. The overwrite property is required for writing data over data already written on a recording medium. It is therefore difficult to obtain a sufficient overwrite property.
In Japanese Patent Application Laid-open Hei 8-249614 (1996) a technique is disclosed wherein the shape of the top pole layer is such that the width gradually increases from the throat height zero position to the point where the top pole layer width starts to increase greatly. However, the technique is provided for having the magnetic flux saturated almost simultaneously between the throat height zero position and the point where the top pole layer width starts to increase greatly. Therefore this structure does not prevent the flux from saturating near the throat height zero position.
As disclosed in Japanese Patent Application Laid-open Hei 7-262519 (1995), frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex, that is, the crest of the coil. Next, a photoresist is applied on the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and other portions such as 7 to 10 xcexcm or above. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm over the apex, a photoresist film having a thickness of 8 to 10 xcexcm or more, for example, is formed below the apex since the fluid photoresist goes downward.
To form a pole portion having a smaller width, it is required to form a frame pattern whose width is about 1.0 xcexcm through the use of a photoresist film. That is, it is required to form a minute pattern having a width of 1.0 xcexcm or below through the use of a photoresist film having a thickness of 8 to 10 xcexcm or above. However, it is extremely difficult to form a photoresist pattern having such a thickness into a reduced pattern width in a manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the bottom electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may be out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern. As a result, the sidewall of the top pole layer may have a round shape and so on and it is impossible to form the top pole layer into a desired shape. If the top pole layer 116 is to be formed into a shape as shown in FIG. 40, in particular, in the region near the interface between the pole portion 116a and the yoke portion 116b, the rays reflected off the bottom electrode film include not only vertical reflected rays but also rays in slanting directions and rays in lateral directions from the slope of the apex. Those reflected rays of light affect exposure of the photoresist layer and the photoresist pattern width that defines the pole width is thereby likely to become greater than a desired width.
It is a first object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for achieving an optimal overwrite property even when the pole width is reduced.
In addition to the first object, it is a second object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for precisely controlling the pole width even when the pole width is reduced.
A thin-film magnetic head of the invention comprises: a medium facing surface that faces a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions placed in regions of the magnetic layers on a side of the medium facing surface, the pole portions being opposed to each other, the magnetic layers each being made up of at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; a thin-film coil at least part of which is placed between the first and second magnetic layers; and an insulating layer for insulating the first and second magnetic layers from the thin-film coil. At least one of the magnetic layers includes: a main layer including one of the pole portions an end of which is placed in the medium facing surface and a yoke portion magnetically coupled directly or indirectly to the other end of the pole portion; and an auxiliary layer magnetically connected to the main layer and provided for increasing the thickness of part of the magnetic layer in the neighborhood of a portion connecting the pole portion to the yoke portion so that the thickness is greater than the thickness of the other part of the magnetic layer.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a medium facing surface that faces a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions placed in regions of the magnetic layers on a side of the medium facing surface, the pole portions being opposed to each other, the magnetic layers each being made up of at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; a thin-film coil at least part of which is placed between the first and second magnetic layers; and an insulating layer for insulating the first and second magnetic layers from the thin-film coil. The method includes the steps of forming the first and second magnetic layers, the gap layer, the thin-film coil, and the insulating layer, respectively. The step of forming at least one of the magnetic layers includes: the step of forming a main layer including one of the pole portions an end of which is placed in the medium facing surface and a yoke portion magnetically connected directly or indirectly to the other end of the pole portion; and the step of forming an auxiliary layer magnetically connected to the main layer and provided for increasing the thickness of part of the magnetic layer in the neighborhood of a portion connecting the pole portion to the yoke portion so that the thickness is greater than the thickness of the other part of the magnetic layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the auxiliary layer increases the thickness of part of the magnetic layer in the neighborhood of the portion connecting the pole portion to the yoke portion so that the thickness is greater than the thickness of the other part of the magnetic layer.
In the thin-film magnetic head or the method of manufacturing the same of the invention, the yoke portion may be greater than the one of the pole portions in width.
In the head or the method an end of the auxiliary layer closer to the medium facing surface may be placed in the neighborhood of an end of the insulating layer closer to the medium facing surface.
In the head or the method edges of the main layer extending in the direction intersecting the medium facing surface may include: first portions extending from the medium-facing-surface-side end of the main layer to the neighborhood of the medium-facing-surface-side end of the insulating layer; and second portions adjoining the first portions. The first portions are orthogonal to the medium facing surface. The second portions extend outward in the direction of width, each forming a specific angle with the first portions. In this case the specific angle preferably falls within a range between 90 and 120 degrees inclusive.
In the head or the method the pole portion and the yoke portion of the main layer may be either made up of one layer or made up of separate layers. If the pole portion and the yoke portion are made up of separate layers, the layer including the pole portions, the layer including the yoke portion, and the auxiliary layer may overlap one another.
In the head or the method the auxiliary layer may be placed between the two magnetic layers. In this case the auxiliary layer may be placed between the insulating layer and the one of the magnetic layers.
In the head or the method the main layer may further include an intermediate portion placed between the pole portion and the yoke portion and magnetically connected to the pole portion and the yoke portion. The width of the intermediate portion is between that of the pole portion and that of the yoke portion.
In the head or the method an end of the intermediate portion closer to the medium facing surface may be placed in the neighborhood of an end of the insulating layer closer to the medium facing surface.
In the head or the method edges of the pole portion extending in the direction intersecting the medium facing surface may be orthogonal to the medium facing surface. At the same time edges of the intermediate portion adjoining the edges of the pole portion may extend outward in the direction of width, each forming a specific angle with the edges of the pole portion. The specific angle preferably falls within a range between 90 and 120 degrees inclusive.
In the head or the method the intermediate portion may have a part uniform in width. The intermediate portion may have a part tapered down to the medium-facing-surface-side in width.
In the head or the method the intermediate portion and the auxiliary layer may overlap each other.
In the head or the method the main layer may include: a first layer including the pole portion and part of the intermediate portion; and a second layer including the yoke portion and the other part of the intermediate portion. In this case the first layer, the second layer and the auxiliary layer may overlap one another.
In the head or the method the auxiliary layer may have a shape approximating to at least part of the intermediate portion. Other and further objects, features and advantages of the invention will appear more fully from the following description.